New findings on ocean warming: 5 questions answered

The ocean absorbs about 90 percent of the excess heat produced as climate change warms the earth.

Editor’s note: A new study by scientists in the United States, China, France and Germany estimates that the world’s oceans have absorbed much more excess heat from human-induced climate change than researchers had estimated up to now. This finding suggests that global warming may be even more advanced than previously thought. Atmospheric scientist Scott Denning explains how the new report arrived at this result and what it implies about the pace of climate change.

How do scientists measure ocean temperature and estimate how climate change is affecting it?

They use thermometers attached to thousands of bobbing robots floating at controlled depths throughout the oceans. This system of “Argo floats” was launched in the year 2000 and there are now about 4,000 of the floating instruments.

About once every 10 days, they cycle from the surface to a depth of 6,500 feet, then bob back up to the surface to transmit their data by satellite. Each year this network collects about 100,000 measurements of the three-dimensional temperature distribution of the oceans.

The Argo measurements show that about 93 percent of the global warming caused by burning carbon for fuel is felt as changes in ocean temperature, while only a very small amount of this warming occurs in the air.

The new study finds that since 1991, the oceans have warmed about 60 percent faster than the average rate of warming estimated by studies summarized by the IPCC, which are based on data from Argo floats. This is a big deal.